1. Field of the Invention
The invention relates to a machine tool having a spindle and having a tool changer for conveying tool holders between a magazine position and a working position on the spindle while substantially maintaining the orientation of the tool holders, the tool holders being held in grippers provided on the tool changer.
2. Description of Related Prior Art
A machine tool of the aforementioned kind is known from U.S. Pat. No. 4,932,118.
In the known machine tool, the magazine position is located above the working position, and in a front view of the machine tool is laterally offset with respect to the working position. Two gripper arms are pivot-mounted on opposite sides of the working position. The gripper arms are moved by means of a linkage and a rocker element, so as to cross over one another, along locus curves whose common starting and end points are the magazine position and working position, respectively. When the one gripper arm is conveying a tool holder from the magazine position to the working position, the other gripper arm is bringing a tool holder from the working position to the magazine position. This known tool changer allows fast tool changing times and a compact construction for the machine tool, since the tool holders are moved past one another at relatively close distances during the changing operation.
The mechanism, consisting of the linkage and the rocker element, that leads to such locus curves is, however, of relatively complicated construction.
A further machine tool in which the transfer position and the working position lie in a common vertical plane is known from U.S. Pat. No. 5,451,196. The tool changer of this machine tool also has two gripper arms, which are coupled by means of a linkage in such a way that their locus curves run, in the region between the working position and the magazine position, at a lateral distance from the vertical plane.
This known tool changer also has a relatively complicated construction. In particular, the linkage joining the two gripper arms has a series of complex articulation arrangements.
The gripper arms of these two known machine tools are configured as parallelogram guides, so that the tool holders are conveyed from the magazine position to the working position and back while retaining their vertical orientation.
With machine tools of this kind it is generally desirable to minimize tool changing times, the intention being for the changer mechanism construction to be as compact and malfunction-resistant as possible. It is also desirable to protect the changer mechanism as far as possible from flying chips and sprayed drilling fluid.